Lithium-ion batteries are a type of rechargeable battery in which a lithium ion moves between a negative electrode and a positive electrode. Lithium ion batteries are commonly used in consumer electronics. In addition to uses for consumer electronics, lithium-ion batteries are growing in popularity for defense, automotive, and aerospace applications due to their high energy density.
FIG. 1 illustrates a top plan view of a conventional lithium ion battery 10 that may be used in automotive applications having an electrode assembly 12 and a pouch 14, which may be formed with an interior region 16 for receiving the electrode assembly 12. The components of the electrode assembly 12 and pouch 14 are illustrative of the basic components and not intended to be depicted in proper orientation or scale.
The electrode assembly 12 may include a first electrode plate 20, a second electrode plate 30, and a separator 40 arranged between the first and second electrode plates 20 and 30 to prevent a short circuit between the first and second electrode plates 20 and 30 and allowing only lithium ions to pass through it. The electrode assembly 12 may be formed by winding the first electrode plate 20, the separator plate 40, and the second electrode plate 30 into a jelly roll type structure. Alternatively, as shown in FIG. 1, the first electrode plate 20, the separator 40, and the second electrode plate 30 may be sequentially laminated into a stack structure. The first electrode plate 20 may be a negative electrode, while the second electrode plate 30 may be a positive electrode, although the reverse arrangement is contemplated. A liquid electrolyte 45 is also introduced within the interior region 16 of the pouch 14 prior to the pouch 14 being sealed.
A positive tab 50 and a negative tab 52 electrically connected to the respective electrode plates 20, 30 of the electrode assembly 10 may be installed such that a predetermined length of them may be exposed outside the case pouch 14. Portions of the electrode tabs 50 and 52 that come in contact with the case pouch 14 may be wrapped with an insulating tape (not shown).
The positive electrode 20 may be formed by coating a strip shaped metal plate such as a positive collector with a positive active material. In one exemplary embodiment, the metal plate may be made of an aluminum film, while the positive active material may be formed from a lithium based oxide as a main component, a binder, and a conductive material. The positive electrode 20 may be electrically connected to a positive tab 50 and wrapped with insulating tape (not shown).
The negative electrode 30 may be formed by coating a strip shaped metal plate such as a negative collector with a negative active material. The metal plate may be made of a copper film while the negative active material may be formed from a carbon material as a main component, a binder, and a conductive material. The negative electrode 30 may be electrically connected to the negative tab 52 and wrapped with insulating tape (not shown).
The separator 40 may be made of a polyethylene film, a polypropylene film, or a combination thereof. The separator 40 may be formed to be wider than the positive and negative plates 20 and 30 to prevent a short circuit between the positive and negative plates 20 and 30.
The liquid electrolyte 45 may include solid lithium salt electrolytes such as LIPF6, LIBF4, or LIClO4, and organic solvents such as carbonate. The liquid electrolyte 45 conducts lithium ions, which acts as a carrier between the negative electrode 30 and the positive electrode 20 when the battery 10 passes an electric current through an external circuit.
The pouch 14 may be formed from a wide variety of materials that are both flexible and heat sealable such that no air or water vapor may enter. The pouch 14 may be a laminate material consisting of aluminum and plastic.
Both the positive electrode 20 and negative electrode 30 are materials into which and from which lithium can migrate. When a cell is discharging, the lithium is extracted from the negative electrode 20 and inserted into the positive electrode 30. When the cell is charging, the reverse process occurs: lithium is extracted from the positive electrode 30 and inserted into the negative electrode 20.